1. Field of the Invention
Aspects of the present invention relate to an organic light emitting display apparatus which can minimize brightness reduction, minimize an increase in power consumption, and reduce or remove motion blurring, and a method of driving the organic light emitting display apparatus.
2. Description of the Related Art
In general, light emitting display apparatuses display images using self-emissive devices. Such light emitting display apparatuses are classified into inorganic light emitting display apparatuses having a light emitting layer formed of an inorganic material, and organic light emitting display apparatuses having a light emitting layer formed of an organic material.
In an organic light emitting display apparatus, electrons and holes are injected into an organic thin film through cathodes and anodes, and are recombined to form excitons or photons to emit light having a specific wavelength. The organic thin film has a multi-layer structure including a hole transport layer, a light emitting layer, and an electron transport layer, to improve the light-emitting efficiency. Also, the organic thin film includes an electron injection layer, a hole injection layer, or something similar, to improve the injection efficiency of electrons or holes and to distribute the electrons and holes uniformly.
Methods of driving the organic light emitting display apparatus are classified into a passive matrix method and an active matrix method. In the passive matrix method, lines are formed to intersect each other when anodes and cathodes are formed in an organic light emitting display apparatus. The lines are then sequentially selected and driven. The organic light emitting display apparatus driven as such by way of the passive matrix method has a simple structure which can be easily implemented. However, an organic light emitting display apparatus operated using the passive matrix method consumes large amounts of power when used to drive a large screen, and a driving (or light emitting) time of each light emitting device is short.
In the active matrix method, on the other hand, the amount of current which flows through respective light emitting devices is controlled using active devices. The active devices may be thin film transistors (TFTs). An organic light emitting display apparatus operated using the active matrix method consumes small amounts of power and has a long driving (or light emitting) time. However, the organic light emitting display apparatus operated using the active matrix method has a motion blurring problem.
Motion blurring is a phenomenon in which pictures (or images) overlap or appear blurry when pictures move on the screen. Motion blurring affects organic light emitting display apparatuses and liquid crystal display apparatuses that use the active matrix method of operation. However, impulse type display apparatuses, such as cathode ray tubes (CRT), are not affected by motion blurring effects.
In impulse type display apparatuses, after-images (blurry images) are reduced by momentarily displaying light corresponding to an amount of brightness required to display each pixel, as illustrated in FIG. 1. In the case of hold type display apparatuses, after-images are easily increased by continuously displaying light corresponding to an amount of brightness required to display each pixel during a constant time period, as illustrated in FIG. 2.
In order to reduce motion blurring in the hold type display apparatuses, a driving method similar to the driving method of the impulse type display apparatuses, such as the CRT display, has been developed. FIG. 3 is a graph illustrating one impulse type driving method that is applied to a related art hold type display apparatus. Referring to FIG. 3, to drive the hold type display apparatus, black frame images are inserted between successive frame images in order to mimic the impulse type driving method.
However, such a driving method suffers from a reduction in an average brightness of the entire screen by the amount of the inserted black frame images. To address this problem, a current flowing through light-emitting diodes of the hold type display apparatus is increased when moving pictures are to be displayed. However, increasing current flow increases power consumption.